Recently, De Smedt and colleagues [32,33] demonstrated that in a subgroup of T-ALL and T-LBL pediatric patients who were poor responders to dexamethasone treatment, leukemia cells are characterized by the expression of the oncogenic kinase PIM1 via JAK1/2 and STAT5 Y694 phosphorylation and that the inhibition of PIM1 makes these cells sensitive to GC. This evidence concerns the gene JAK1 and leukemia.